Without being bound by any particular theory, recent studies in ophthalmology suggest that presbyopia that arises almost universally among people in their 40s is the result of the continued growth of the lens. Lens growth results in shortening the length between the lens and ciliary muscles. This compromises the ability of the ciliary muscles to effectively stretch the lens. This is exhibited as a reduced amplitude of accommodation. Increasing the effective working distance between the ciliary muscles and the lens equator is effected by increasing the diameter of the sclera in the region of the ciliary body. This theory is not confirmed and other or additional factors may obtain.
Astigmatism is another prevalent visual problem. Astigmatism occurs when light entering the eye is “split” into two separate parts instead of focusing to one, precise point on the retina. Astigmatism usually occurs because of a corneal irregularity. Historically, a lens with two different power curves (toric lens) has been employed to correct astigmatism. In practice, these lenses have a variable edge profile that is thinner in some places and thicker in others. Some amounts of astigmatism are corrected surgically in patients with astigmatism alone or astigmatism present with nearsightedness. There is no present procedure to correct astigmatism combined with farsightedness.
The cornea accounts for about 70% of the eye's focusing power. By altering the shape and power of the cornea, the optical characteristics of the eye can be changed. This is the basis for most refractive surgical procedures.
In the practice of this invention, astigmatism (with or without near or farsightedness) is ameliorated by placement of stents proximate to but not in the corneal visual pathway.
The sclera is an element of the fibrous tunic of the eye (along with the cornea). The sclera ranges from about 0.13 to 1 mm in thickness. The tendons of the eye muscles insert on the sclera.